(1) Field of the Invention
The present invention relates to an image formation supervisory control system including an image forming apparatus and a supervisory control unit connected to the image forming apparatus for mutual communication, and to a method for supervising such an image forming apparatus using the supervisory control unit.
(2) Related Art
An image forming apparatus for business use, such as a copying machine and a printer, is often shared by several sections in one firm. In such a case, it is necessary to control the number of copies made by each section for budget planning and other purposes.
In conducting the above control operation, a control apparatus, such as a computer, is connected to one or more image forming apparatuses via a telephone line and the like, so as to transmit various kinds of information between the control apparatus and the image forming apparatuses. In a system shown in FIGS. 1A and 1B, for instance, the upper limit is set to the number of copies each section is allowed to make, while making more than the limit number of copies is prohibited.
In FIGS. 1A and 1B, copying machines 1000A to 1000C and a host computer 2000 are connected via a telephone line 3000. An identification code assigned to one section (hereinafter referred to as "section ID") is registered in each of the copying machines 1000A to 1000C beforehand. A section ID inputted by a user is compared with the registered section ID, and if both section IDs are identical, the inputted section ID is transmitted to the host computer 2000 via the telephone line 3000.
The host computer 2000 monitors the current total number of copies made by each section. When a section ID is received from one of the copying machines 1000A to 1000C via the telephone line 3000 and the current total number of copies made under the section ID is smaller than the upper limit number of copies predetermined for the section ID, the host computer 2000 permits a copying operation to the copying machine into which the section ID has been inputted.
The copying machine, to which the copying operation is allowed, informs the host computer 2000 of the number of copies after the copying operation. The host computer 2000 adds the number of copies to the total number of copies made by the section. If the addition result is larger than the upper limit number, copying will be prohibited under the section ID.
In the conventional copying machine supervisory control system described above, the number of copies made by each copying machine is sent to the host computer after the copying, and added to the total number of copies already stored in the host computer. Since copying under the section ID is permitted until the total number of copies made by the section reaches the upper limit number, the total number of copies made by the section is already larger than the upper limit number when each copying machine is prohibited from copying under the section ID. For this reason, the conventional copying machine supervisory control system fails to strictly control the number of copies made by each section.
In the case where the host computer permits a first copying machine to perform a copying operation under a section ID and receives the same section ID from a second copying machine while the first copying machine is performing the copying operation, the host computer permits the second copying machine to perform a copying operation, because the host computer has not been informed of the number of copies from the first copying machine in this stage, and the total number of copies made by the section has not surpassed the upper limit number.
In such case, the number of copies increases at both copying machines, and when the host computer is informed of the number of copies, the total number of copies surpasses the upper limit number even further, spoiling the setting of the upper limit number to control the number of copies made by each section.